Here is a rough idea of what would have worked for me. This is a personal opinion and everyone is different, so make your own list from here!
Socks (2 pairs would ensure you don´t get blisters..if you wanna try! Thin layer and hiking layer)
Hiking boots (the most sturdy the better support for your foot and ankle)
Bra for girls
Shirt. I prefer the one covering the shoulders personally as I don´t like when my backpack sticks to my skin but up to you.
Hat for the moments you are in the sun.
Sunglasses (I would say optional though! Depends how much sun you will have on your trek)
Insect repellent and sunscreen
Trekking poles if you have. Will save pressure on your knees.
Small pack (25 to 30 litres)
A pair of flip-flops
4 t-shirts (nothing dries there, you will be happy to have a dry shirt in the morning! On the second day, I was so wet that I even changed shirt at lunch time!)
3 pair of socks (or double that if you use double socks – base liners and hiking ones)
2 shorts if you have
2 or even 3 bras. Again..nothing dries there!
1 long pant for the evening although you could stay in shorts
1 leggings to keep you warm during the second night which is next to Ciudad Perdida so a bit colder
1 long sleeve
1 silk bag, so nice to sleep in it when the mattress is a bit mouldy because it can´t dry easily there
A small liner bag adding warmth if you have
2 to 3 liters of water. In a camelbak if you have, itis very handy and ensures that you drink constantly during the day
Magnesium tablets if think you may have cramps
1 swimming suit put at the top of the bag as one hour after you start walking you will grab it. One is enough as it doesn´t matter if it stays wet considered you will jump in the water immediately when you put it!
A pareo or long towel that will be super handy to change into your swimming suit and back into your clothes in the middle of 50 people. I wish I had taken one and lucky another girl had one!
A towel, micro-fibre is nice as it is light and small
A small mini micro-fibre towel handy to dry your feet when you cross rivers
2 dry bags or even more. One dry bag to put your clothes in and one to put your wet clothes in. Bin bags can do the job.
Dry bag to put your camera in if needed
Bin bag to put on top of your backpack to protect from the rain even if you have a raincover – or not if your raincover is good enough
An environmental friendly soap in its container
Toothbrush small toothpaste
No need for wipes or detol, you will swim in rivers often!
An after sun and anti-mosquito bite cream
A first-aid kit. Even if the guides carry some, I would still take mine. Mine is about 600grams. For diarrhea, headaches, cuts, you know those products well, take them with you. In particular a remove-ticks!
Some card game or some Schweinerei game!
earplugs in case people snore. we were lucky people didn´t.
no need for an eye-protection as you will wake up before sunrise!
That´s it for now. Will review this list with people who came on my trek to ask them if they have anything to add to it!